Screwless quick system for connecting a lead connector to a generator of an implantable medical device

ABSTRACT

A screwless quick connection system for connecting a lead connector to a generator of an active implantable medical device is shown and described. The connector head includes a housing receiving a plug of a lead connector. A mechanism for locking the plug into the housing is provided by a U-folded leaf spring. Each branch of the U is provided with a respective hole sized so that the plug passes through the holes on both branches when it is inserted into the housing. The blade is deformable between a free state, in the absence of plug, and a deformed state, with the plug inserted therein. In the free state, both holes are misaligned, while in the deformed state they are aligned. In this way, an edge of both holes exerts by reaction a radial stress force against the smooth outer surface of the plug inserted therein.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/100,634, filed May 4, 2011, which claims the benefit of priority toFrench Application No. 10/53446 entitled “Screwless Quick ConnectionSystem Of A Lead Connector To A Generator Of An Implantable MedicalDevice” and filed May 4, 2010, both of which are hereby incorporated byreference herein in their entireties.

BACKGROUND

The present invention relates to an active implantable medical device asdefined by the Jun. 20, 1990 directive 90/395/CEE of the EuropeanCommunity Council, including those devices that continuously monitor apatient's cardiac activity and, if necessary, deliver to the heartelectrical pulses for stimulation, cardiac resynchronization,cardioversion and/or defibrillation, in response to a rhythm disorderdetected by the device, and those devices such as neurological devices,cochlear implants, drug pumps, and implanted biological sensors.

Active implantable medical devices include a housing that is generallydesignated as “the generator.” The generator is mechanically andelectrically connected to one or more “leads” that bear on them one ormore electrodes that contact those tissues to which it is desirable todeliver electrical pulses, e.g., to apply stimulation pacing pulses,and/or to collect (detect) an electrical signal. These tissues include,for example, myocardial, nerve, and muscle tissue.

The French standard NF EN 50077 and its international counterpart ISO5841-3, Implants for Surgery—Cardiac Pacemakers—Part 3: Low-ProfileConnectors (IS-1) for Implantable Pacemakers, defines a normalizedconnection system standard in the industry, which is identified as“IS-1”. The IS-1 standard ensures interchangeability and compatibilityof the leads and generators produced by different manufacturers. In thisregard, it should be understood that the present invention is notlimited to the particular case of a connection system according to theIS-1 standard, nor even to connection systems applicable to cardiacpacemakers.

Typically, the connection between a lead connector—hereafter more simplyreferred to as “plug”—and a connector of a generator is made by one ormore screws that are tightened by the surgeon using an ad hoc tool(e.g., a screwdriver, possibly equipped with a torque limiter) at thetime of implantation of the device and/or the lead. This known screwconnection system has several drawbacks. First, in addition to requiringa specific tool for its implementation, this system requires thepresence of caps provided with sealed slots through which the tool mustpass to prevent the terminals from coming into contact with body fluidsafter implantation. This requirement for sealing the slots through whichthe tool passes increases the cost and requires a volume or size of thegenerator at the connector that is large enough to accommodate the tool.

Second, a screw connection system does not prevent from a screwingoversight, whether from an insufficient screwing or from anovertightening of the screw and damaging the device, by the surgeon.

Third, a screw connection system also introduces significant risks ofdamage to the silicone plug by the screwdriver with a consequent loss ofinsulation, of removal or stripping of the screw thread at the time ofits use, of binding thereof, or of damage to the head of the screw incase of incorrect insertion of the screwdriver.

From an economic standpoint, the use of a screw system generates certainadditional costs (e.g., manufacturing of the screw, threading ofinserts) and requires providing with the medical device a special tool(e.g., a screwdriver with torque limiter) for tightening the screw. Froman industrial standpoint, the use of a screw connector system requiresan operation for inserting and adjusting the position of screws in apredetermined position during the packaging of the device, and ofaddition of a spot of glue to freeze this position of the screw. From asafety standpoint, the operation of screwing the screw by the physicianto secure the plug requires special attention, with an implementationtime large enough to make sure that the plug is maintained in thehousing, precisely and durably.

Despite these acknowledged drawbacks, the screw connection system isstill almost universally used. Indeed, the connectivity standardsrelated to implantable medical devices require (i) minimum retentionforces sufficient to prevent accidental disconnection at the time ofimplantation or during the product lifetime, and (ii) a high-quality andenduring electrical contact (i.e., a very low contact resistance)between the connector plug of the lead and the electrical terminal ofthe implantable device. These two mechanical and electrical requirementsare particularly well satisfied by a conventional screw connectionsystem, despite its many disadvantages.

Various other systems for securing the plug into the housing of theconnector head have been proposed to overcome the many difficulties anddrawbacks outlined above.

Thus, EP 0890371 A1 and its counterpart U.S. Pat. No. 6,112,120, bothassigned to Sorin CRM S.A.S., previously known as ELA Medical, describeseparating the electrical contact and mechanical retention functions.The electrical contact is ensured by a spring system exerting a radialpressure against the conductive surface of the plug. The mechanicalretention of the plug in the housing is secured by a locking wedgeinserted between the body of the plug and the housing wall at the outletthereof.

Another solution is proposed by EP 0900577 A1 (assigned to Sorin CRMS.A.S., previously known as ELA Medical), which implements a lockingsystem with a retractable spring-loaded eccentric, locally appliedagainst the plug and bearing against it response to an attemptedextraction.

These solutions are functionally effective, but they involve relativelycomplex, and therefore expensive to produce, mechanical systems (e.g.,including elements such as a spring, eccentric, and slide). They alsorequire a specific release mechanism for the removal of the plug,typically requiring the use of a special tool for removing the holdingor retraction force provided by the eccentric. Finally, they requirespecial precautions to durably ensure the efficient sealing required atthe connector.

Other known efforts at alternative connection systems implementdeformable elastic elements such as metal blades with one or moreorifices through which the plug passes when inserting it into the slot,and exerting a radial point of contact between the edge of the orificeand the surface of the plug.

Thus, U.S. Pat. No. 5,252,090 (Giurtino et al.) proposes to block theplug with an elastically deformable metal piece, extending around theplug in a plane substantially radial to the axis of the plug. Deformabletabs formed in the part produce by stemming an anti-kickback effect,preventing any withdrawal or pulling of the plug once it is inserted inthe metal part. For disassembly, the part is extended laterally by twosymmetrical ears that, by pinching, deforms the piece enough to removethe tabs of the plug and release it. This device is very effective interms of mechanical retention. However, unlocking the device requireshaving two entrances on each side of the part, to ensure a symmetricalpinching, and therefore requires providing two release buttons (one oneach side of the head connector).

FR 2 662 310 A (Darby et al.), refers to an elastic clamp whose ends ofthe two arms are folded against one another and are provided with holescorresponding to the diameter of the plug. The holes are shifted whenthe clamp is in the free state, and they can be aligned by moving thetwo arms of the clamp. The plug can then be introduced through the twoholes, and be retained in the clamp after release of the force exertedto bring the two arms together. This connection system is very effectivein terms of mechanical retention of the plug, but it is not designed tobe integrated with a generator. Rather, it is presented to serve as adispensing connector between several leads, this connector being placedaway from the generator.

SUMMARY

It is therefore, an objective of the present invention to provide agenerator for an active implantable device including a connector headprovided with a connecting system for the plug of a lead that is bothsimple and effective and that would:

-   allow connection and disconnection of the plug to the connector    terminal without screws and without ad hoc tools;-   establish a strong mechanical connection ensuring an effective and    permanent retention of the plug, even in the case of plugs with    smooth surfaces such as those carried out in accordance with the    IS-1 standard mentioned above; and-   be integrated into the very small volume of the connector head of an    implant, so as to be minimally invasive for the patient.

Broadly, the present invention is directed to a leaf spring systemwhich, by its geometric characteristics and the nature of the materialused, can provide a tool-free system for securing a plug when it isinserted into the connector housing of the generator of the device witha specific geometry for ensuring the mechanical action oflocking/unlocking the plug from one only side of the generator.

One embodiment of the invention is a device in which the connector headincludes, in a manner in itself known, for example, according to the FR2 662 310 A cited above, at least one female housing provided with anelectrical connection terminal and able to receive a plug, the plughaving, for example, a smooth surface of a cylindrical or prismatic leadconnector, and locking means for the mechanical immobilisation of theplug in the housing. The locking means preferably has a resilient memberadapted to be deformed and placed under elastic tension when insertingthe plug into a slot in the housing in which the resilient member isdisposed. The resilient member also is adapted to be deformed afterinsertion of the plug, the elastic deformation then being in an axialdirection, such that the resilient member comes to exert a retentionforce on the plug. This retention force in the radial direction exertscontact pressure against the smooth surface of the plug far exceeds theforce of insertion of the plug into the housing, and opposes anextraction force applied to the plug. The device also includes structurefor releasing the locking means, able to apply to the resilient member,due to an external force, a mechanical force to neutralize the retentionforce and thereby permit an extraction of the plug from the housing.

In one embodiment, the resilient member is a leaf spring folded to havea generally U-shaped portion including a central region at the base ofthe U and two legs or branches of the U extending from the centralportion. A first branch preferably extends in a plane in a firstdirection forming a first angle with respect to an axial direction ofinsertion of the plug into the slot, and a second branch preferablyextends in a plane in a second direction forming a second angle withrespect to the axial direction of insertion. The two branches areelastically connected in the central region of the U and extend from thecentral region to a respective end, and each branch is provided with arespective hole sized so that the plug can pass through the holes whenthe plug is inserted into the slot.

The leaf spring is thus deformable between a free state or unstressedposition, in the absence of a plug, and a deformed state or stressedposition, with the plug inserted. In the free position, the projectionsof the two holes in the first and second branches in the planeperpendicular to the axial direction of insertion are overlapping butmisaligned, while in the stressed position the projections are aligned,so that one edge of each hole crossed by the plug exercises, by areaction effect of the deformed leaf spring, a radial stress forceagainst the smooth outer surface of the plug, thereby producing saidcontact pressure and a retention force.

The first branch may in particular extend in a direction primarilyperpendicular to the axial direction of insertion and the second branchin a direction, primarily oblique to, forming, for example, an anglebetween 45° and 75° from, the axial direction of insertion.

In a first embodiment, the end of one branch of the U-shaped portion isa stationary end relative to the head of the connector, and the end ofthe other branch is a free end that is extended by a flange which servesas a support element. In an alternate embodiment, an auxiliary elasticbody may be interposed between the connector body and the central regionof the U at the junction of the two branches.

In a second embodiment, the end of one of the branches of the U-shapedportion is a free end extended by a flange serving as a support element,the end of the other branch is a pivoting end moving over the head ofthe connector, about an axis perpendicular to the axial direction ofinsertion, and a resilient return member is further inserted between theconnector body and the central region of the U at the junction of thetwo branches.

In either embodiment, the flange is advantageously a flat push-buttonextending in a plane generally or substantially parallel to the axialdirection of insertion, which can notably extend into an internal cavityof the connector head, this cavity being isolated in a sealed mannerfrom the outside environment. The flange may also include an elementcausing a tactile response to the change of state between the free andstressed positions.

Preferably, the leaf spring is a metal blade connected to a terminal formaking an electrical connection, between the lead and the generator, soas to achieve simultaneous mechanical immobilization of the plug in thehousing and electrical connection of this plug to the connectionterminal of the generator.

Advantageously, the present invention provides a quick screwlessconnector system that is handled via a single support, located on onlyone side of the connector head (for the lock as well as for the unlockoperation). Further, the present invention locking means is sealedvis-à-vis the outside world, that is to say that no bodily fluid thatwould promote a loss of electrical insulation or corrosion can leak intothe housing through the locking means. It also is simple to manufactureand inexpensive to industrialize. In addition to providing a mechanicalconnection, it also provides an electrical connection between theterminal of the generator and the plug with, in this case, asufficiently low contact resistance (in accordance with the industrystandards in force for electrical contact resistance, for example, forstimulation/detection below 5 Ohms for static and below 10 Ohms fordynamic resistance, and for defibrillation below 0.5 Ohm for static and1 Ohm for dynamic resistance), and during the useful life of theproduct. The present invention also is well suited to manual use by adoctor equipped with gloves, with appropriate forces needed to lock orunlock the plug, and a use that is not affected by the environment inwhich the device is used (blood medium in particular). Moreover, theinvention realizes a reduction of the metal mass used, providing animproved electromagnetic compatibility of the device, and a lever armeffect of reducing the effort needed from the doctor for locking andunlocking the plug and, conversely, producing with an equal force agreater contact force between the connector and the plug, therefore lesselectrical resistance at the point of contact.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, characteristics and advantages of the presentinvention will become apparent to a person of ordinary skill in the artfrom the following detailed description of preferred embodiments of thepresent invention, made with reference to the drawings annexed, in whichlike reference characters refer to like elements and in which:

FIG. 1 is an elevated perspective of a generator partially cutaway toshow a lead tip for an implantable cardiac device inserted into aconnection system in accordance with the present invention;

FIG. 2 is an isolated view of the connector head of the device of FIG. 1showing in exploded view the leaf spring before introduction into theslot;

FIG. 3 is a detail view in perspective of the underside of the leafspring of FIG. 1;

FIG. 4 a and FIG. 4 b illustrate a first embodiment of the presentinvention showing the leaf spring in the free state at the beginning ofintroduction of the plug, and the deformed state once the plug iscompletely inserted and stressed into place by the leaf spring,respectively;

FIG. 5 a and FIG. 5 b are perspective views corresponding to respectiveconfigurations of FIG. 4 a and FIG. 4 b;

FIG. 6 a and FIG. 6 b are similar to FIG. 4 a and FIG. 4 b, for a secondembodiment of the present invention; and

FIG. 7 a and FIG. 7 b are counterparts of FIG. 5 a and FIG. 5 b, for thesecond embodiment of the invention.

DETAILED DESCRIPTION

Preferred embodiments of a device according to the present inventionwill now be described with reference to FIGS. 1-7,

In FIG. 1, reference 10 generally designates a generator of the device,a cardiac pacemaker given here as an example of any device to implementthe teachings of the invention.

Generator 10 includes a body 12 enclosing the various electroniccircuits and power source (e.g., a battery), coupled with a connectorhead 14. In the example shown, connector head 14 is intended toaccommodate two different leads and therefore contain the connectionterminals (not shown) having conductive elements embedded in theinsulating body of the connector head 14, for example, made of epoxyresin.

To allow insertion of lead tips, each of which comprising electricalconnection elements, the connector head 14 includes female housings orslots 16, 18 (also visible in FIG. 2) in which the proximal end 20 ofthe lead is introduced, as shown in FIG. 1.

The lead is, e.g., a bipolar lead including a lead according to the IS-1standard mentioned above. This lead has at its distal end 20 a firstsmooth and cylindrical conductive surface 22, herein simply referred toas “plug”. This plug is protected by a first insulating sheath 24 (alsoshown in FIG. 3) with peripheral reliefs 26 and 28 to ensure a sealingfunction vis-à-vis the external environment when the end of the lead isfully inserted into the corresponding slot 16 of connector head 14. Inthe case of a bipolar lead, the end 20 carries a second conductivesurface, coaxial and shifted from the first (not shown), and protectedby a second insulating sheath.

The present invention relates to the mechanical retention of the end 20of the lead once it is fully inserted into the corresponding housingslot 16 or 18. It should be understood, however, that the presentinvention is not, prima facie, the electrical connection betweenconductive surfaces of the plug and the connection terminals of theconnector head, because these two functions can be separated. Instead,the present invention focuses on the mechanical locking of the lead end(plug) into the connector head slot. It also should be understood thatthe plug need not have a smooth and cylindrical conductive surface,although that is a preferred and standard construction.

Advantageously, the electrical connection and mechanical locking may beprovided by a common element (e.g., a metallic blocking conductive partelectrically connected to the circuits of the generator). In otherwords, the invention is equally applicable in the case wherein theelectrical connection is provided by a separate element from the oneensuring the mechanical retention and in the case wherein the sameelement performs these two functions.

In the illustrated example, the mechanical retention of the lead tip 20in its housing is ensured by the distal end, that is to say by the plug22, an area where the diameter of the plug is the smallest. The distalend 22 is generally in the shape of a cylindrical metal surface, but thepresent invention can be extrapolated by a person of ordinary skill inthe art to other materials, conductive or not, and other shapes,including prismatic shapes instead of cylindrical shapes.

Retention of the plug is secured by a leaf spring 30 shown in detail inFIG. 2, and FIG. 3, FIG. 4 a, FIG. 4 b, FIG. 5 a, FIG. 5 b (for a firstembodiment) and in FIG. 6 a, FIG. 6 b, FIG. 7 a and FIG. 7 b (for asecond embodiment).

This leaf spring 30 is made of an elastically deformable material, forexample, a spring steel. It has a generally U-shaped geometry comprisinga first branch 32, on the plug insertion side, and a second branch 34,on the opposite side, with the two branches being united by a centralregion 36.

The first branch 32 extends in a plane substantially normal to the Zdirection of insertion of the plug (also referred to as the “Z axis ofinsertion”), as illustrated in FIGS. 1 and 4 b. The end 38 of the firstbranch is provided with structure to immobilize it relative to theconnector head, which can be, for example, pins or lugs that engage thehousing. The second branch 34 is in a plane that is oblique to the Zaxis of insertion, with an inclination angle of about 45° to 750. Thesecond branch 34 is extended at its end by a flattened surface 40,hereinafter simply designated as a “flange”, extending in a planesubstantially parallel to the Z axis of insertion.

The leaf spring 30 is provided with two holes whose dimensions areadapted to receive the plug 22, with a hole 42 in the first branch 32and a hole 44 in the second branch 34 located approximately vis-à-visthe hole 42. In a preferred embodiment, the hole 42 (on the branch 32approximately normal to the axis of insertion) is a circular hole whosedimensions correspond to the diameter of the plug 22, except for thedimensional tolerances. For example, for an IS-1 distal plug, thedimension is 1.59+/−0.03 mm, and for a DF1 distal plug, the dimension is1.25+/−0.03 mm. The hole 34 (the second branch 44 which extendsobliquely to the Z axis of insertion) is an oblong hole, so that it canalso be crossed, except the dimensional tolerances, by the plug insertedalong the Z axis of insertion.

As can be seen in greater detail in FIG. 4 a and FIG. 4 b, the holes 42and 44 are slightly shifted with respect to each other when the leafspring is in the free state, that is to say in the absence of anyexternal forces and before insertion of the plug 22 (see FIG. 4 a).However, these holes are aligned when the plug is inserted, the leafspring 30 then being in a deformed state of elastic stress (see in FIG.4 b). This alignment of the holes geometrically defines a channelthrough which the cylindrical plug 22 can be inserted, housed and keptin place.

The leaf spring 30 may be made by folding of a metal strip or blade ofconstant or variable thickness, with a sheet thickness typically between0.4 and 0.6 mm. A variable thickness allows taking advantage of therelative stiffness differences associated with the different thicknessesof leaf spring 30. The various cuts, including holes 42 and 44, arepreferably made in the metal blade which it is flat and the metal bladeis then folded into the desired U-shape and inspected (e.g., for properstiffness, and position of holes). The bending radius of the centralregion 36 and of the region connecting the second leg 34 to the flange40 is preferably about 1.5 times the thickness at this location. It isalso possible to stamp some zones to locally stiffen the metalstructure. The material used is preferably a medical implantable gradematerial, e.g., a 316 LVM stainless steel or titanium.

The metal blade thus produced is introduced into a cavity 46 formed inthe connector head 14, the latter being preferably made by molding amedical implantable grade polymer material, e.g., Tecothane (trademark)1075 DM. The molding can directly form the cavity 46 which opens intoone of the two housings 16, 18 for receiving the plug, providing also agroove 48 receiving the lugs 38 of the end of the first branch 32 of theleaf spring 30. These grooves can thus secure this end, furtherproviding guidance, direction and positioning of the leaf spring 30 inthe connector head 14.

Alternatively, instead of mounting the leaf spring 30 in the polymerblock of the connector head, it is possible to mount it in anintermediate part, for example, a shaped cage, which will later beincorporated in and/or bonded to a proper location of the connectorhead.

To ensure sealing after placement of the leaf spring 30, the housing 46is sealed by a flexible cover (not shown) of elastomer or plastic,secured to the connector head 14 by known techniques. For example, aseal of silicone adhesive can be deposited at the interface between theconnector head 14 and the flexible cover, or the cover can be crimpedusing a seam framework set in the connector head or ultrasonicallywelded, to prevent any liquid infiltration.

The flexible cover allows the transmission of a force pressing on theflange 40 of the leaf spring 30, e.g., by a practitioner's finger. Thismaneuver, performed through a flexible element, eliminates any sealingproblem in connection with locking/unlocking the plug.

Preferably, the connector head 14 is provided with as many cavities andleaf springs as there are lead ends to be coupled to the device. In theexample shown, on one side of connector head 14 is a cavity 46 forreceiving a leaf springblade 30 for blocking the proximal end of thelead (plug) inserted into the cavity 18. A configuration of the sametype is carried on the opposite side (not visible) of the connector headto immobilize the lead tip to be inserted into the cavity 16. Thus, oneof the leaf springs 30 is arranged on one side of the connector head(visible in FIG. 2), the other being disposed on the opposite lateralface (not visible in FIG. 2). The practitioner thus has two supportzones with two different buttons, one on each side of the connectorhead, to lock/unlock either one or the other of the two lead tips, by amaneuver executed with only one finger on either side of the connectorhead 14.

As shown in the bottom view of FIG. 3, the flange 40 preferablycomprises on one side a “tactile” device that is like a pushbutton,allowing the practitioner to feel a “click” at end of the supportmovement when the mechanism is sufficiently engaged, and another “click”when he releases the pressure from the support zone of the pushbutton onflange 40.

The mechanical principle of the invention will now be explained withreference to FIG. 4 a, FIG. 4 b, FIG. 5 a and FIG. 5 b, as part of afirst embodiment (corresponding to FIGS. 1-3 described above).

The principle of tightening results of the deformation of the leafspring 30: by exerting pressure (arrow 52, FIG. 4 a) on the pushbuttonof flange 40, the user flexes (arrow 54, FIG. 4 a) the second obliquebranch 34 at an oblique angle to insertion axis Z whose end is free.This action thus aligns the oblong hole 44 of the second branch 34 andthe cylindrical hole 42 of the first branch 32 disposed in a planeessentially normal to insertion axis Z. The plug 22 can then be inserted(arrow 56, FIG. 4 a). In the final position corresponding to a fullinsertion, the pressure 52 on the pushbutton of flange 40 is released sothat the leaf spring 30 tends to return to its original position, but iscompletely prevented due to the presence of the plug 22 through the hole44 (configuration of FIG. 4 b).

The plug 22 is thereby clamped through a process of “amplified rubbing”to control the retention force and to avoid any undesired disconnection.Specifically, the leaf spring 30 applies a normal force on the plug 22at contact points 58 and 60 of the first branch 32 and second branch 34,respectively, thus creating the phenomenon of adhesion between the twomechanical surfaces (that of the leaf spring and that of the plug). Fromthe point of view of statics, this configuration can be described by afriction cone of angle Φ characteristic of the friction coefficient fbetween the two surfaces, the boundary conditions being given byƒ=arctan(Φ). The geometry of the leaf spring blade helps maintain theplug in place because any attempt to remove the plug causes at theplug/leaf-spring interface a change of orientation of the normal forceat contact points 58 and 60. Due to friction any withdrawal force intangential projection is opposed by a greater retention force opposingthe withdrawing motion.

Preferably, the geometric configuration can even cause a mechanicalphenomenon of jamming the plug 22 in leaf spring 30 in case of attemptedwithdrawal, with such a gripping force that any movement will beeffectively prevented, while maintaining the static balance of forces:whatever the intensity of external mechanical actions, the biasgenerated by the deformation of the leaf-spring 30 causes jamming of theplug 22. The conditions for this jamming can be calculated according toknown methods, taking into account the parameters constituted by thecoefficient of friction f (depending on the type of materials used), theguide length L between the two contact points 58 and 60, the diameter ofthe plug and the diameter of the holes 42 and 44.

The blocking of the plug by the leaf spring blade 30 is in any casereversible. In this regard, a new pressure (arrow 62, FIG. 4 b) on thepushbutton of flange 40 allows for a relative movement of branch 34 andprovides free passage to pull back the plug (arrow 64, FIG. 4 b) or toreposition it.

In an advantageous embodiment, the elastic properties of tactilefeedback device 50 described above with reference to FIG. 3 can be usedto amplify by leveraging the force exerted by the leaf spring blade 30on the plug 22 after the latter has been introduced.

Alternatively or in addition, to further increase the retention force ofthe leaf spring blade 30, it is possible to add to the pushbutton offlange 40 a layer of elastomer material which deforms to allow passageof the plug 22, bringing by reaction extra force at the leaf springblade to maintain the end of the plug 22 fixed in position.

A second embodiment of the present invention is described with referenceto FIG. 6 a, FIG. 6 b, FIG. 7 a and FIG. 7 b, which are counterparts ofFIG. 4 a, FIG. 4 b, FIG. 5 a and FIG. 5 b. In this second embodiment,the end of the second branch 34 is not a free end, but rather one endmounted on pivot 66 in the connector head, for example, by means of twolugs 38 (visible on FIG. 7 a and FIG. 7 b) mounted without embeddinginto a corresponding homologous groove of the connector head.

The end of the first branch 32, in turn, is a free end equipped with theflange 40 on which the blocking support (arrow 52, FIG. 6 b) or releasesupport (arrow 62, FIG. 6 b) will be exercised. The configuration alsoincludes a fixed elastomer pressure cushion 68 (e.g., placed at thebottom of the cavity receiving the leaf-spring 30) and supporting thecentral region 36 of the U of the leaf-spring 30.

Under the effect of a pressure force (arrow 52) exerted on the firstbranch 32, the leaf-spring 30 pivots around the connection 66 at theopposite end of the branch, and deforms while releasing the passage ofplug 22 through holes 42 and 44 along insertion axis Z.

Once the plug 22 is inserted and the force 52 is removed, the plug 22 isblocked under the force of friction at the contact points with the edgesof holes 42 and 44, according to the same principle as that describedabove in connection with the first embodiment. The deformed elastomercushion 68 generates a permanent opposing force that helps maintain theplug 22 tight and increases the retention force (arrow 70, FIG. 6 b).

To release the plug 22, the maneuver is similar: a push (arrow 62, FIG.6 b) on the flange 40 causes, against the resisting force of theelastomer cushion 68, a pivot (arrow 72, FIG. 6 b) of the leaf spring30, which deforms again, releasing the retention force previously heldon the plug 22 and allowing plug 22 to move.

One skilled in the art will appreciate that the present invention can bepracticed by other than the embodiments described herein, which areprovided for purposes of illustration and not of limitation.

1. A connector head for coupling a lead to a generator body, theconnector head comprising: at least one housing for receiving a plug endof a lead along an axis of insertion; an elastic element configured toreceive and immobilize the plug in the housing, wherein the elasticelement comprises a U-shaped leaf spring having a first branch and asecond branch, the first and second branches having respective first andsecond holes that allow the plug to be inserted through the first andsecond holes in the housing; wherein the U-shaped leaf spring isdeformable between a free state, wherein the leaf spring is in a neutralposition, and a deformed state, wherein the leaf spring takes on anexpanded position; wherein in the free state, the projections of thefirst and second holes in a plane perpendicular to the axis of insertionare misaligned; wherein in the deformed state the projections of thefirst and second holes in the plane perpendicular to the axis ofinsertion are sufficiently aligned to receive an inserted plug so thatan edge of each of the first and second holes contact the plug insertedtherein and exert a radial stress force against the plug, producing aretaining force against extraction of the plug in a direction oppositeto the insertion; and wherein the elastic element further comprises arelease mechanism configured to receive an external force on the elasticelement to neutralize said retaining force and thereby permit a removalof the plug from the housing.
 2. The connector head of claim 1, whereinthe release mechanism is a flange at a free end of one of the firstbranch and the second branch of the U-shaped leaf spring.
 3. Theconnector head of claim 2, wherein the flange comprises a flattenedpushbutton extending in a plane substantially parallel to the axis ofinsertion.
 4. The device of claim 2, wherein the flange comprises anelement causing a tactile response to the change of state between thefree and deformed states.
 5. The connector head of claim 1, wherein therelease mechanism is configured such that the external force on therelease mechanism causes expansion of the U-shaped leaf spring.
 6. Theconnector head of claim 1, wherein in the free state, the projections ofthe first and second holes in a plane perpendicular to the axis ofinsertion are overlapping but misaligned.
 7. The connector head of claim1, wherein the first branch extends along a plane that is substantiallyperpendicular to the axis of insertion.
 8. The connector head of claim1, wherein the second branch extends along a plane that is substantiallyoblique to, forming an angle in a range selected from between 45′ and75° from, the axis of insertion.
 9. The connector head of claim 1,wherein the generator comprises an electrical connection terminal andthe leaf spring comprises a metal blade connected to the electricalconnection terminal, so as to simultaneously achieve the mechanicalimmobilization of the plug in the housing and the electrical connectionof the plug to the electrical connection terminal.
 10. The connectorhead of claim 1, wherein the connector head comprises more than onehousing for receiving in the connector head more than one plug end ofthe lead, and wherein the connector head comprises more than one elasticelement for receiving the more than one plug end.
 11. The connector headof claim 10, wherein a first plug end is received by a first leaf springpositioned on a first side of the connector head and a second plug endis received by a second leaf spring positioned on a second side of theconnector head opposite the first side.
 12. A method for receiving andretaining a lead in a connector head of a generator body, the methodcomprising: providing a connector head comprising: a housing forreceiving a plug end of a lead along an axis of insertion; and anelastic element configured to receive and immobilize the plug in thehousing, wherein the elastic element comprises a U-shaped leaf springhaving a first branch and a second branch, the first and second brancheshaving respective first and second holes that allow the plug to beinserted through the first and second holes in the housing; wherein theU-shaped leaf spring is deformable between a free state, wherein theleaf spring is in a neutral position, and a deformed state, wherein theleaf spring takes on an expanded position; wherein in the free state,the projections of the first and second holes in a plane perpendicularto the axis of insertion are misaligned; wherein the elastic elementfurther comprises a release mechanism configured to receive an externalforce on the elastic element; exerting a pressure on the releasemechanism to deform the leaf spring from the free state to the deformedstate, such that the first and second holes in a plane perpendicular tothe axis of insertion are aligned to receive the plug end of the lead;inserting the plug end of the lead into the housing and through thefirst and second holes of the leaf spring; and retaining the plug end ofthe lead in the housing by releasing the pressure on the releasemechanism, wherein releasing the pressure causes the leaf spring to movetowards the free state, thereby causing an edge of each of the first andsecond holes to contact the plug inserted therein and exert a radialstress force against the plug, and thereby producing a retaining forceagainst extraction of the plug in a direction opposite to the insertion;wherein the leaf spring is prevented from fully achieving the free statewhen the plug end is inserted in the first and second holes.
 13. Themethod of claim 12, further comprising exerting a second pressure on therelease mechanism to deform the leaf spring to the deformed state suchthat the plug end of the lead can be extracted from the first and thesecond holes.
 14. The method of claim 12, wherein in the free state, theprojections of the first and second holes in a plane perpendicular tothe axis of insertion are overlapping but misaligned
 15. The method ofclaim 12, wherein retaining the plug end of the lead in the housingfurther provides an electrical connection between the lead and thegenerator.
 16. The method of claim 15, wherein the generator comprisesan electrical connection terminal and the leaf spring comprises a metalblade connected to the electrical connection terminal, so as tosimultaneously achieve retaining the plug in the housing and theelectrical connection of the plug to the electrical connection terminal.17. The method of claim 12, further comprising inserting a plug end of asecond lead into a second housing having a second leaf spring in theconnector head, and retaining the plug end of the second lead in thesecond housing by the second leaf spring.
 18. An implantable medicaldevice comprising a generator and connector head, the connector headcomprising: a housing for receiving a plug of a lead connector; alocking mechanism for locking the plug into the housing, wherein thelocking mechanism comprises a folded leaf spring; wherein each branch ofthe leaf spring is provided with a hole sized to receive the plugtherethrough when the plug is inserted into the housing; wherein theleaf spring is deformable between a free state in the absence of theplug and a deformed state with the plug inserted through the hole ineach branch of the leaf spring; wherein the leaf spring takes on anexpanded position in the deformed state; and wherein the holes aremisaligned in the free state and substantially aligned in the deformedstate such that when a plug is inserted into the housing an edge of bothholes exerts by reaction a radial stress force against an outer surfaceof the plug inserted therein.
 19. The implantable medical device ofclaim 18, wherein the locking mechanism further comprises a releasemechanism configured to receive an external force to deform the leafspring into the deformed state.
 20. The implantable medical device ofclaim 19, wherein the release mechanism is configured to receive theexternal force by a maneuver on only one side of the connector head.